The experience in Western Europe suggests that overreliance on institutional stability hinders trade union revitalization. This paper explores the other side of this coin: what is the impact of dismantling industrial relations institutions on union revitalization? It investigates the drivers and outcomes of the main revitalization strategies used by trade unions in Hungary and Romania as a response to the frontal attack of governments on their institutional supports post-2008. In both countries, national-level confederations took political action seeking to amend the labour laws that undermined their role and influence. At the company and occupational level, some trade unions increased their organizing efforts to retain their influence under an adverse legal framework. This article reveals that deinstitutionalization can be a driver of revitalization when trade unions are willing to take small steps to strengthen their links with rank-and-file members and with other unions, social movements or international organizations by using a combination of revitalization strategies. It also shows that unions have to simultaneously draw on different sets of power resources, particularly a mixture of organizational and societal power resources, to revitalize after losing institutional resources.